The present invention relates to systems used for laminating semiconductor wafer substrates with dry film resist (DFR) and systems used for removing a PET (polyethylene terepthalate) support film from the wafer substrates after the DFR laminating step. More particularly, the present invention relates to a system which is capable of both laminating DFR on a semiconductor wafer substrate and removing the support film from the substrate at the same location without the need to transfer the substrate between two separate stations for these purposes.
In the fabrication of semiconductor integrated circuits, metal conductor lines are formed on a silicon wafer substrate to interconnect the multiple components in device circuits on the semiconductor wafer. A general process used in the deposition of metal conductor line patterns on semiconductor wafers includes deposition of a conducting layer on the silicon wafer substrate; formation of a photoresist or other mask such as titanium oxide or silicon oxide on the conductive layer, in the form of the desired metal conductor line pattern, using standard lithographic techniques; subjecting the wafer substrate to a wet or dry etching process to remove the conducting layer from the areas not covered by the mask, thereby leaving the metal layer in the form of the masked conductor line pattern; and removing the mask layer typically using reactive plasma and chlorine gas, thereby exposing the top surface of the metal conductor lines. Typically, multiple alternating layers of electrically conductive and insulative materials are sequentially deposited on the wafer substrate, and conductive layers at different levels on the wafer may be electrically connected to each other by etching vias, or openings, in the insulative layers and filling the vias using aluminum, tungsten or other metal to establish electrical connection between the conductive layers.
Deposition of conductive layers on the wafer substrate can be carried out using any of a variety of techniques. These include oxidation, LPCVD (low-pressure chemical vapor deposition), APCVD (atmospheric-pressure chemical vapor deposition), and PECVD (plasma-enhanced chemical vapor deposition). In general, chemical vapor deposition involves reacting vapor-phase chemicals that contain the required deposition constituents with each other to form a nonvolatile film on the wafer substrate. Chemical vapor deposition is the most widely-used method of depositing films on wafer substrates in the fabrication of integrated circuits on the substrates. Copper is one of the most widely-used conductive layers in semiconductor fabrication due mainly to the inherent superior conductivity of copper as compared to aluminum and other metals.
Several lithograpic methods are known for forming a circuit pattern in a conductive layer on a wafer substrate. These include laminating a photoresist material, such as by using a dry film resist (DFR), on the conductive layer; using a visible light laser to irradiate the photoresist material in the form of the desired circuit pattern image; and then subjecting the irradiated wafer substrate to a developer, which selectively dissolves non-irradiated portions of the photoresist material and leaves irradiated portions of the photoresist material intact to form a mask corresponding to the circuit pattern. The masked substrate is then subjected to a wet or dry etching process, in which those areas of the conductive layer not covered by the mask are etched and those areas of the conductive layer covered by the mask remain unetched. Finally, the mask is removed such as by using plasma or reactive chlorine gas to expose the unetched metal circuit layer.
One of the most common materials for preparing a photoresist mask on a wafer substrate includes photopolymerizable elements, or dry film resists (DFRs), which are typically transferred from a DFR tape onto the conductive layer on the wafer substrate. A multi-layered construction of a typical DFR tape is generally indicated by reference numeral 1 in FIG. 3 and includes a support film 4 such as polyethylene terepthalate (PET). A photopolymerizable DFR layer 3 is provided on the PET support film 4, and a polyethylene protective film 5 may be provided on the DFR layer 3. The DFR layer 3 is applied to the wafer substrate by first removing the protective film 5 from the DFR tape 1 to expose the DFR layer 3. The DFR layer 3 and the PET support film 4 are then applied to the conductive layer on the wafer substrate 36. Finally, the PET support film 4 is removed from the underlying DFR layer 3.
FIG. 1 illustrates a typical conventional DFR laminating system 10 for laminating a DFR layer 3 and a PET protective film 4 on the wafer 36. The DFR laminating system 10 typically includes a rotatable tape supply reel 14, from which extends a segment of the DFR tape 1. The DFR tape 1 extends between a guide roller 23 and a nip roller 16, which removes the protective film 5 from the DFR layer 3 of the DFR tape 1, and the protective film 5 extends from the nip roller 16 and typically around a pair of guide rollers 18 and 20, respectively, and is collected on a protective film wind reel 22. The tape 1, with the protective layer 5 removed therefrom, is advanced between a laminating head 24 above and a vertically-extendible wafer support table 12 below thereof, and extends around a pair of remove head rollers 28 of a remove head 26. Accordingly, the wafer support table 12 initially receives an unlaminated wafer 36 having a conductive layer (not illustrated) such as copper deposited thereon. The remove head 26 and laminating head 24 initially move to the left in FIG. 1 to extend the DFR tape 1 above the surface of the wafer 36, at which time additional DFR tape 1 is simultaneously unwound from the rotating tape supply reel 14. Next, the wafer support table 12 raises the wafer 36 into contact with the DFR tape 1. As it moves to the right, the laminating head 24 then heat-presses the DFR tape 1 against the conductive layer (not illustrated) on the wafer 36, whereupon the DFR layer 3 is laminated onto the conductive layer of the wafer 36 and the PET support film 4 remains on the DFR layer 3 on the wafer 36. A laser 34 is then used to cut a portion of the DFR layer 3 and the PET support film 4 from the DFR tape 1, around the periphery of the wafer 36, such that the DFR layer 3 and PET support film 4 remaining on the wafer 36 substantially conform to the size and shape of the wafer 36. The remove head 26 is then moved to the right in FIG. 1 to remove the DFR tape 1 (consisting of the residual PET support film 4 and residual DFR layer 3 from which the PET support film 4 and DFR layer 3 portions, respectively, laminated onto the wafer 36 were cut) from the wafer 36, after which the DFR tape 1 is advanced first between the remove head rollers 28 of the remove head 26 and then between a pair of guide rollers 30, and finally, collected on a used tape wind reel 32. The wafer support table 12 is then lowered and the wafer 36, having the DFR layer 3 and PET support film 4 laminated thereon, is removed therefrom.
Referring next to FIG. 2, after it is removed from the wafer support table 12 of the DFR laminating system 10, the laminated wafer 36, having both the DFR layer 3 and the PET support film 4 laminated thereon, is transferred to a PET removing system 40 and placed on a vertically-extendible wafer support table 12 to remove the PET support film 4 from the DFR layer 3 on the wafer 36 for further processing of the wafer 36. The PET removing system 40 typically includes a tape supply reel 42, from which is extended a segment of adhesive tape 7. The adhesive tape 7 extends over a guide roller 44 and around the bottom arc of a tape applicator head 46, and upwardly between the adjacent remover head rollers 49 of a remover head 48. The adhesive tape 7 may further extend around guide rollers 50, 52 and between an additional pair of adjacent guide rollers 54 before winding on a used tape wind reel 58. Accordingly, after positioning of the laminated wafer 36 on the support table 12, the wafer support table 12 raises the wafer 36 as the remover head 48 is moved to the leftmost position in FIG. 2 and a length of the adhesive tape 7 is unwound from the tape supply reel 42. The tape applicator head 46 initially contacts the leftmost edge of the PET support film 4 on the wafer 36. As the remover head 48 is moved to the right in FIG. 2, the tape applicator head 46 presses the adhesive tape 7 against the PET support film 4 and removes the PET support film 4 from the underlying DFR layer 3 as the tape applicator head 46 traverses the width of the wafer 36. The adhesive tape 4, with the PET support film 4 removed from the wafer 36 adhering thereto, is finally wound on the used tape wind reel 58.
One of the limitations inherent in operation of the conventional DFR laminating system 10 and the temporally- and spatially-separate PET removing system 40 is that the laminated wafer 36 must be removed from the wafer support table 12 of the DFR laminating system 10 and transferred to the wafer support table 12 of the PET removing system 40 for removal of the PET support film 4 from the wafer 36. This results in accumulation of significant lag time between the processes in the treatment of multiple semiconductor wafers 36 over time. Furthermore, since the laminating process and the PET film removal processes require separate stations in the clean room, the equipment for the two systems occupies a much greater volume of valuable clean room space than would be needed if the systems were consolidated into a single system for performing both functions.
Accordingly, an object of the present invention is to provide a system for consolidating the DFR wafer laminating and support film removal processes in a semiconductor fabrication facility.
Another object of the present invention is to provide a system and method for increasing the wafer per hour (WPH) throughput of wafers processed in a semiconductor fabrication facility.
Still another object of the present invention is to provide a system and method for both laminating a conductive layer on a semiconductor wafer substrate with a dry film resist (DFR) layer and removing a typically polyethylene terepthalate (PET) support layer from the DFR layer.
Yet another object of the present invention is to provide a dry film resist laminating and PET removal system which consolidates valuable footprint space in a semiconductor production facility clean room.
A still further object of the present invention is to provide a system which saves time and space in the laminating of a dry film resist (DFR) layer on a semiconductor wafer substrate and removal of a support film such as polyethylene terepthalate (PET) from the dry film resist layer for further processing of the wafer.
In accordance with these and other objects, the present invention includes a DFR laminating and film removing system which is capable of both laminating a dry film resist (DFR) layer on a semiconductor wafer and removing a DFR support film such as polyethylene terepthalate (PET) from the DFR layer on the wafer at a single location. The DFR laminating and support film removing system of the present invention comprises a support film removing head for removing a portion of support film from the semiconductor wafer substrate after the support film portion and dry film resist (DFR) portion are laminated from a DFR tape onto the wafer and before the laminated DFR portion is cut from the DFR tape.